The invention relates to a miniaturized x-ray source situated in a catheter that generates x-rays while minimizing risk from exposure to the x-rays.
Traditionally, x-rays have been used in the medical industry to view bone, tissue and teeth. X-rays have also been used to treat cancerous and precancerous conditions by exposing a patient to x-rays using an external x-ray source. Treatment of cancer with x-rays may cause well documented side effects, many of which are due to the broad exposure of the patient to the therapeutic x-rays.
To improve medical treatment and diagnosis of patients, minimally invasive endoscopic techniques have been developed and are used to treat a variety of conditions. Endoluminal procedures are procedures performed with an endoscope, a tubular device into the lumen of which may be inserted a variety of rigid or flexible tools to treat or diagnose a patient""s condition.
The desire for improved minimally invasive medical devices and techniques have led to the development of miniaturized x-ray devices that may be used in the treatment or prevention of a variety of medical conditions. International Publication No. WO 98/48899 discloses a miniature x-ray unit having an anode and cathode separated by a vacuum gap positioned inside a metal housing. The anode includes a base portion and a projecting portion. The x-ray unit is insulated and connected to a coaxial cable which, in turn, is connected to the power source. An x-ray window surrounds the projecting portion of the anode and the cathode so that the x-rays can exit the unit. The x-ray unit is sized for intra-vascular insertion, and may be used, inter alia, in vascular brachytherapy of coronary arteries, particularly after balloon angioplasty.
International Publication No. WO 97/07740 discloses an x-ray catheter having a catheter shaft with an x-ray unit attached to the distal end of the catheter shaft. The x-ray unit comprises an anode and a cathode coupled to an insulator to define a vacuum chamber. The x-ray unit is coupled to a voltage source via a coaxial cable. The x-ray unit can have a diameter of less than 4 mm and a length of less than about 15 mm, and can be used in conjunction with coronary angioplasty to prevent restenosis.
Miniaturized x-rays are not foolproof, however, and still present difficulties upon use. The x-ray unit generates heat, which can damage adjacent healthy tissue. Additionally, the x-rays are not localized and irradiate local tissue rather than only irradiating the desired tissue. It is difficult to maintain the positioning of these instruments at the desired location. Improvedminiaturizedx-ray units that overcome these difficulties are desirable.
Other techniques are used to treat tumors with radiation, including planting a seed of radioactive material at the tumor site, a procedure that is typically accomplished with endoluminal procedures. However, the patient becomes xe2x80x9chotxe2x80x9d, i.e., radioactive, and the procedure risks exposure of the medical personnel to radiation.
As noted above, many types of cancerous and precancerous conditions are treated by externally irradiating the tumor or site with x-rays. However, the x-rays are broadcast over a large area of healthy tissue in addition to the tumor because the radiation is administered from outside the body so that it penetrates the skin and any internal organs or tissue to reach the desired site. To avoid this, miniaturized x-ray systems which generate x-rays at the desired site are a desirable alternative to conventional apparatus.
Since many types of cancer occur in a body cavity or lumen, such as in the rectum, vagina, esophagus or pulmonary passages, it would be desirable to treat these cancers using miniaturized x-ray sources in combination with endoscopic techniques, which are minimally invasive to the patient, so that the cancer or other intraluminal tissue is directly treated with x-rays. This technique would minimize exposure of healthy tissues to the x-rays.
The present invention overcomes the difficulties associated with x-ray therapy and apparatus of the prior art by providing an endoscopic x-ray device that generates x-rays at the site of treatment and minimizes exposure of other tissues to irradiation.
A miniaturized x-ray apparatus for delivering x-rays to a selected site within a body cavity includes a catheter having at least one lumen and an x-ray transparent window at a distal end thereof; an x-ray source in the lumen adjacent said x-ray transparent window; a movable x-ray shield positioned to direct x-rays from the source through the x-ray transparent window to the selected site. The x-ray device ranges from 2 mm to about 15 mm.
The x-ray source is positioned inside an x-ray shielded catheter lumen, i.e., the catheter lumen is impenetrable by x-rays except in the area of the x-ray transparent window which is described in more detail below.
The x-ray source includes a cathode and an anode and an insulating material. The anode and cathode are separated by a vacuum gap. Insulating material may surround the base anode and cathode.
Preferably, a separate lumen of the catheter includes a camera through which medical personnel may observe the body lumen and procedure.
In a preferred embodiment, inflatable (anchoring or positioning) balloons are provided on the exterior of the endoscope to maintain the desired position of the instrument once inserted into the lumen. These balloons may be filled with a gas via catheter lumens connected to a gas or fluid source. Preferably, the balloons are filled with a fluid that absorbs x-rays so that the fluid will help prevent irradiation of undesired tissue. The gas and or fluid will also preferably help to absorb heat generated during the procedure to prevent burning of local tissue. A thermocouple may be positioned on the exterior of the endoscope to monitor the temperature at the treatment site.
In an alternative embodiment, the catheter includes an x-ray source and the anchoring balloons which are inflatable with gas or fluid as described above. This embodiment does not include a shield.
Another alternative embodiment provides a catheter having a miniaturized x-ray device and a stationary x-ray shield having an x-ray transparent window.
The invention is described in further detail hereinbelow.